WTf is set theory?

Question

if U stands for element of

then


if A U B and B U C

then A U C


That's pretty easy...is this what set theory is?

Answer 1

Well, U looks nothing like the set membership symbol ∈. More importantly, though, A∈B ∧ B∈C does NOT imply that A∈C. Example: let A=∅, B = {∅}, and C = {{∅}}. Then A∈B ∧ B∈C, but A∉C, as C has only the single element B. The fact that set membership is not, in general, transitive, is what gives sets their structure, and keeps them from becoming undifferentiated blobs.

Answer 2

"WTf is set theory"
can't you ask a question without wtf included?

"if U stands for element of "
no, it doesn't stand for that, it is reunion


"if A U B and B U C

then A U C "
this doesn't make sense

"That's pretty easy"
no, it's not because it doesn't make sense


"is this what set theory is?"

to get an idea what set theory is:
http://en.wikipedia.org/wiki/Set_theory